Duct seal assembly

Abstract

A flexible, fluid-tight seal assembly for sealing the gap between a duct and a wall where the duct passes through an opening in the wall. The seal assembly includes an annular housing affixed to and centered on the opening in the wall. The housing includes a circular recess opening inwardly toward the duct. Contained in the recess is a carrier ring supporting a set of three O-rings set into cooperable O-ring grooves in the carrier ring. One O-ring groove opens inwardly toward the duct such that the associated O-ring snugly encircles the duct so as to provide a seal between the duct and the carrier ring. The other two O-rings are set into grooves which face in opposite directions such that the two O-rings snugly abut the walls of the recess to provide a seal between the carrier ring and the housing. The carrier ring is movable laterally in the recess of the housing so as to permit lateral movement of the duct with respect to the wall. Also, the O-ring sealed between the carrier ring and the duct permits the duct to undergo axial motion with respect to the carrier ring and the wall. Together, the three O-rings also permit the duct to undergo limited rotational motion about axes of rotation lying in the plane of the wall opening and extending transversely with respect to the duct. The seal assembly provides an effective gas- and liquid-tight seal between the duct and the wall and may be particularly adapted to accommodate a hot air duct in an airplane.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: 
     
       1. A seal assembly for forming a fluid-tight seal between a duct and a wall where the duct passes through an opening in the wall sufficiently large to permit the duct to move laterally within the opening, comprising: an annular housing affixed to said wall about said opening in said wall so as to form a passage through which said duct passes, said passage being sufficiently large to allow said duct to undergo lateral movement within said passage relative to said wall, said housing including means forming a circumferential internal recess that opens radially inwardly toward said duct and which includes mutually opposing, substantially parallel interior sidewalls extending generally parallel to the plane of said wall; and   a substantially circular carrier ring engaged in said recess of said housing, said carrier ring having a first circumferential O-ring groove opening radially inwardly and supporting a first elastomeric O-ring snugly received in said first groove, said carrier ring and said first O-ring being sized such that said first O-ring snugly encloses in sealing relationship an exterior surface of a duct passing through said opening in said wall, said carrier ring further including at least one circumferential O-ring groove opening radially with respect to the axis of said carrier ring and supporting an elastomeric O-ring sized to snugly abut an interior facing sidewall of said recess to provide a seal between said carrier ring and said housing, said recess of said housing being sized larger in diameter than the diameter of said carrier ring so as to provide radial clearance for relative lateral motion of said duct and said carrier ring with respect to said housing.   
     
     
       2. The seal assembly defined in claim 1 wherein said carrier ring includes second and third circumferential O-ring grooves each opening in opposite directions axially with respect to the axis of said carrier ring, said second and third O-ring grooves of said carrier supporting second and third elastomeric O-rings engaged in sealing relationship respectively against the opposing sidewalls of said recess. 
     
     
       3. The seal assembly defined in claim 1 wherein said carrier ring includes a second circumferential O-ring groove opening axially with respect to the axis of said carrier ring, said second O-ring grooves supporting an O-ring snugly abutting one sidewall of said recess in sealing relationship, and wherein said carrier ring further includes a substantially planar annular surface opposite said second O-ring groove, said substantially planar annular surface slidably abutting the other sidewall of said recess. 
     
     
       4. The seal assembly defined in claim 2 further comprising a substantially cylindrical spacer element affixed to the external surface of said duct and wherein the size of said spacer element and said carrier ring are such that said first O-ring in said first groove of said carrier ring snugly encloses said spacer element of said duct, said spacer element operating to insulate said carrier ring and said O-rings from high temperatures attendant to transmission of hot gas by said duct. 
     
     
       5. The seal assembly defined in claim 2 wherein said housing comprises first and second annular discs, each of said discs having a substantially circular central opening sized to allow said duct to move laterally within said opening, said annular discs being aligned coaxially and spaced from one another by a tubular spacer having an inside diameter larger than the diameters of said circular openings in said discs such that said discs and said spacer form said recess containing said carrier ring, and means affixing said discs to said spacer and to said wall. 
     
     
       6. The seal assembly defined in claim 2, 4, or 5 wherein said first O-ring groove in said carrier ring has substantially parallel planar side walls and wherein said first O-ring has flattened sides sized to cooperably fit in said first groove to prevent rotation of said first O-ring due to axial motion of said duct. 
     
     
       7. The seal assembly defined in claim 6 wherein said first O-ring is formed of glass fiber reinforced silicone rubber. 
     
     
       8. The seal assembly defined in claim 2 wherein said recess in said housing has a depth less than the radial width of said carrier ring to thereby effectively prevent said duct from abutting said housing during vigorous lateral motion of said duct. 
     
     
       9. The seal assembly defined in claim 4 wherein said recess in said housing has a depth less than the radial width of said carrier ring to thereby effectively prevent said spacer element from abutting said housing during vigorous lateral motion of said duct. 
     
     
       10. The seal assembly defined in claim 3 further comprising a substantially tubular thermally insulating spacer element affixed about said duct, and wherein said first O-ring snugly encircles said spacer element. 
     
     
       11. The seal assembly defined in claims 3 or 10 wherein said carrier ring further comprises a third O-ring groove and associated third O-ring, said second and third O-ring grooves opening in opposite directions such that said second and third O-rings abut the interior facing side wall surfaces of said recess to provide a double O-ring seal between said housing means and said carrier ring. 
     
     
       12. The seal assembly defined in claims 3 or 10 wherein said second O-ring is formed of silicone rubber and wherein said first O-ring is formed of a glass fiber reinforced silicone rubber, said first O-ring having oppositely disposed planar surfaces oriented to lie substantially in the plane of said O-ring, and wherein said first O-ring groove of said carrier ring includes substantially planar parallel sidewalls, said first O-ring and said first O-ring groove being cooperably sized so as to prevent rotation of said first O-ring due to axial movement of said duct. 
     
     
       13. The seal assembly defined in claims 3 or 10 wherein said housing is formed of first and second substantially planar annular discs, said first and second discs being spaced apart by a tubular spacer having an inside diameter greater than the inside diameters of said discs such that said discs and said spacer form said recess containing said carrier ring. 
     
     
       14. The seal assembly defined in claim 3 wherein said recess in said housing has a depth less than the radial width of said carrier ring to thereby effectively prevent said duct from abutting said housing during vigorous lateral motion of said duct. 
     
     
       15. The seal assembly defined in claim 10 wherein said recess in said housing has a depth less than the radial width of said carrier ring to thereby effectively prevent said spacer element from abutting said housing during vigorous lateral motion of said duct.